Like many Americans, Hayden Cook decided long ago who to vote for in this year's presidential election. And yet, every day, the 19-year-old from Wilkes-Barre, Pennsylvania is bombarded with political ads, despite installing a blocker on YouTube and opting out of cable television. "It's still so constant," Cook said. "Work is six minutes away - you're already hearing two or three ads; then we have the radio on at work and there's ads there." More than $10bn (£7.6bn) is expected to be...